1. Field of the Invention
The present invention relates to a method of manufacturing a sheet-prepreg reinforced with fibers and it also relates to an apparatus for the same. The sheet-prepreg of the present invention is used as one kind of industrial materials to form laminated products.
2. Description of the Prior Art
The conventionally-well-known method of impregnating fibers with thermoplastic resin to manufacture fiber-reinforced materials comprises introducing a sheet of fibers such as warp or woven fibers such as fabrics to a roller on which the thermoplastic resin has been coated, transferring the thermoplastic resin on the coating roller to the sheet of fibers or woven fibers, and then contacting the front or back side of the sheet of fibers or woven fibers with heating rollers to enhance resin-impregnating efficiency, as disclosed in preliminarily-opened Japanese Patent Applications Sho 61-229534, -228535 and -228536.
In the case of the apparatus for practicing the above-mentioned conventional method, no air shielding member such as a band belt is positioned on the back side of the fibers or woven fibers sheet which contacts the coating roller and the back side of the fibers or woven fibers sheet is thus left open to air.
The coating roller and a group of the heating rollers which is adjacent to the coating roller are placed separately each other. The resin just extruded is continuously supplied to the coating roller and coated onto the fibers or woven fibers sheet, thereby causing the resin to be transferred to the adjacent heating roller. The resin on the surface of the coating roller seems therefore to be slightly deteriorated but the amount transferred to the surface of the heating roller which is adjacent to the coating roller is extremely small because it is transferred only through the fibers or woven fibers sheet. The resin transferred thus stays on the surface of the heating roller without being transferred to the other heating rollers. Therefore, the resin transferred is not displaced by the one just extruded and maintained, hot and contacting air, on the heating roller. It is extremely difficult to completely remove the resin from the heating roller and the resin thus kept on the heating roller is deteriorated by heat and oxidation and crosslinked further and further as time goes by, thereby causing the apparatus to be rendered inoperative.
The resin impregnated into the fibers or woven fibers sheet has been deteriorated by heat and oxidation, as described above. Therefore, the sheet-prepreg thus obtained has insufficient strength and is poor in quality.